import java.util.Arrays;
import java.util.Scanner;
import  Array
/**
 * Creat with IntelliJ IDEA
 * Description
 * User: mamba24
 * Date: 2022-04-20
 * Time: 19:47
 * To BE A Better Person-2020-3-2
 */
public class Testdemo {
    public static void main(String[] args){
            String str;
        Arrays.sort();
            Scanner sc= new Scanner(System.in);

            while(sc.hasNextLine()){
                str=sc.nextLine();
                char[] arr=new char[str.length()];
                for(int i=0;i<str.length();i++){
                    arr[i]=str.charAt(i);
                }
                for (int i = 0; i < arr.length; i++) {
                    for (int j = i+1; j < arr.length; j++) {
                        if (arr[i] == arr[j]) {
                            arr[j] = '\0';
                        }
                    }
                    if(arr[i]=='\0'){
                        continue;
                    }else{
                        System.out.println(arr[i]);
                    }
                }
            }


    }
}
